Research

Research in our group centres on developing microscopic theories for a variety of experimentally relevant phenomena relating to the electronic and magnetic properties of condensed matter. This encompasses both the vast world of the solid state, be it crystalline or amorphous, as well as topical mesoscopic and nanoscale systems such as quantum dots and molecular electronic devices. The work is very much interdisciplinary, straddling the borders of chemistry, physics and materials.

The essential theoretical theme throughout is that of many-body theory: the quantum and statistical mechanics of ~1023 interacting electrons. Our interests centre on strongly correlated systems, where physical properties are dominated by strong electron interactions; as well as disordered interacting systems where the additional, subtle effects of disorder come into play.

The problem of strongly interacting electrons has been around for more than half a century. It is one of the most challenging and active fields in condensed matter science, and an understanding of it underpins an enormous, diverse range of phenomena. This includes metal-insulator transitions – one example of a so-called quantum phase transition, in this case between an insulating and metallic state and induced, for example, by increasing the pressure of a system; quantum magnetism, whether of intrinsically localised spins or in itinerant electron systems; high-temperature superconductivity; the behaviour of magnetic impurities in non-magnetic metals or insulators; and the physical properties of materials such as heavy Fermion metals or Kondo insulators, whose fascinating and often exotic behaviour derives from the strong electron interactions arising in the localised f-orbitals characteristic of these lanthanide- or actinide-based compounds. Strong electron correlations also play a key role in the electrical transport properties of quantum dots – the single-electron transistor for example; and likewise in the field of molecular electronics, where a single molecule conducts current between two electrodes (‘leads’) as an integral part of nanoscale circuitry.

How does one tackle such problems? So-called ab initio calculations are out of the question: even if computers could deal with ~1023 interacting electrons, one would learn only what the "answer" is, and not why - a far more interesting question. The modus operandi is to develop and study the simplest theoretical models that capture the essential physical behaviour one seeks to understand. But "simplest" is a misnomer: the relevant models are rarely soluble; and one seeks to construct approximate but physically motivated theories, employing a variety of theoretical and computational methods from several areas of condensed matter science, and developing new approaches in the process.

Prospective students may have a background in either chemistry or physics: the work is adaptable to students from different backgrounds, and its intrinsic interdisciplinary nature means that each learns aspects of the other’s trade.

For further information about the members and research activities of the full Oxford Theoretical Chemistry Group, follow this link: